During the hydraulic fracturing or completion of a wellbore that provides access to subterranean, high pressure pumps, a wellhead assembly and various other types of equipment are installed at the wellbore site to enable safe and efficient stimulation operations to allow for the extraction of hydrocarbons and fluids from subterranean formations.
The wellhead assembly provides access to the subterranean formation and has various pressure containing components, various casing strings, casing valves, and fluid conduits. During stimulation operations, the wellhead assembly will have a frac stack/tree, which has a series of large bore valves that provide full access to the tubular casing that traverses a subterranean formation.
Hydraulic fracturing of subterranean formations requires high volumes of fracturing fluids to be pumped to the subterranean formations at high velocities and pressures to fracture the subterranean formation. With emergence of pad drilling, where more than one well exists at a single location providing multiple subterranean access points, a method of operations often referred to as simultaneous operations or zipper frac operations, is used to enhance efficiencies by reducing time and costs to complete each well on a multi-well pad. Simultaneous operations allow for stimulation operations to proceed on one subterranean formation point, while preparing an adjacent subterranean formation(s) for stimulation by running a series of wireline tools to the subterranean formation point where the stimulations operations will proceed after the prior subterranean formation is stimulated completely.
An apparatus can be used in simultaneous operations that allows for fluid(s) and pressure to be directed to the appropriate subterranean formation while isolating fluid(s) and pressure access to another subterranean formation(s). This apparatus is commonly referred to as a zipper manifold. During pumping operations, the zipper manifold is used to contain pressure and direct the fluid to the appropriate well, while isolating the wells that are not being fractured. The zipper manifold opens/closes a series of valves depending on which well(s) need to be isolated and which well needs the frac fluid directed to it.
Fluid(s) at a predetermined pressure is pumped into the manifold. A series of open valves direct fluid(s) and pressure to a subterranean formation, while all other valves on the manifold are closed to isolate adjacent subterranean formation(s) from exposure to fluid(s) and pressure. The operations of opening and closing a series of valves to direct and isolate pressure is conducted many times until all subterranean formation points have been stimulated.
The fluid mixture, volume, velocity and pressure required to fracture subterranean formations is variable depending on the composition of the formation. The combinations of these variables at the subterranean formations dictate the requirements of the horsepower and pumping capacity at the surface. The differential of pressure requirements at the subterranean formation and the requirements at the surface is a result of the fluids undergoing friction loss from the fluids' drag on the inside surface of the pipe, and from obstructions in the fluids' flow path. Obstructions are anything that changes the fluids' velocity and/or direction such as restrictions in the fluids' path, and can occur anywhere in the flow path.
Many difficulties exist when using a zipper manifold to conduct simultaneous operations, such as friction loss from the inner diameter reduction inside the flow path of the zipper manifold. The choking-down of incoming fluid into the manifold increases the pressure needed to overcome the restriction, increases the fluids' velocity, and creates turbulence in the fluids' velocities. In many instances the fluids are transporting proppant which has an abrasive effect on the equipment. The abrasive effect of the proppant is increased exponentially as a result of increased velocity in the equipment, such as when there is a restriction in the fluid flow as the fluid enters the zipper manifold or passes through the various valves in the zipper manifold. The effects of this dynamic are pressure build-ups, additional strain of upstream equipment, equipment damage/failure, and additional safety risks on the jobsite.
Thus, any advance which facilitates a less turbulent flow path, reduces fluid velocity, reduces fluid pressure, and minimizes the effects of friction loss when using a zipper manifold to conduct simultaneous operations would provide a competitive advantage in the industry.